The Plant Maze Challenge: Investigating Phototropism

Materials Needed:

• A cardboard box with a lid (a shoebox works perfectly)
• A few pieces of cardboard (from another box) for the maze walls
• Strong tape or a hot glue gun
• Scissors or a box cutter (with adult supervision if needed)
• A small pot or a plastic cup with drainage holes
• Potting soil
• Fast-growing seeds (bean seeds or grass seeds are excellent choices)
• Water
• A notebook or journal for observations (your "Lab Notebook")
• A pencil or pen

Lesson Overview

Subject: Biology

Grade Level: High School (Age 15)

Time Allotment:

• Day 1: 60 minutes (Introduction and setup)
• Ongoing: 5 minutes daily for 7-14 days (Observation and watering)
• Final Day: 30 minutes (Analysis and conclusion)

Learning Objectives

By the end of this lesson, you (Madison) will be able to:

1. Design and construct a simple light maze to test a biological hypothesis.
2. Explain the concept of phototropism and the role of the plant hormone auxin.
3. Observe and document systematic data on plant growth over time.
4. Analyze experimental results to draw a valid conclusion about how plants respond to light stimuli.

Alignment with Standards

This lesson aligns with the Next Generation Science Standards (NGSS), specifically:

• HS-LS1-2: Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. (Focusing on how a plant's systems respond to external stimuli).
• Science and Engineering Practices: Planning and Carrying Out Investigations; Analyzing and Interpreting Data; Constructing Explanations and Designing Solutions.

Lesson Activities & Instructions

Part 1: The Spark - Introduction & Hypothesis (Day 1 - 15 mins)

Hello Madison! Have you ever noticed how a houseplant on a windowsill seems to "lean" towards the window? It's not just trying to get a better view! Plants are amazing living things that actively respond to their environment. Today, we're going to investigate this behavior.

1. Engage with a Question: In your Lab Notebook, write down this question: "How do plants 'know' where light is coming from?" Jot down a few initial ideas you have. No idea is too wild!
2. Background Knowledge: The phenomenon of a plant growing towards light is called phototropism (photo = light, tropism = turning). This response is controlled by a hormone in the plant called auxin. Auxin collects on the shaded side of the plant stem. It causes the cells on that shaded side to grow longer, which makes the stem bend and curve towards the light source. More light means more energy for photosynthesis!
3. Form a Hypothesis: Now, let's make a formal prediction. In your notebook, write a hypothesis using an "If... then..." format. For example: "If a plant needs light to grow, then it will grow through a maze to reach a light source."

Part 2: The Build - Constructing Your Plant Maze (Day 1 - 30 mins)

This is where your engineering skills come in! Your goal is to create a maze inside the shoebox that forces the plant to grow around obstacles to reach a single light source.

1. Prepare the Box: Stand the shoebox up on one of its short ends. At the very top, use scissors to cut a single hole about the size of a quarter. This will be the only place light can enter.
2. Plant Your Seed: Fill your small pot or cup with soil. Plant 2-3 bean seeds about an inch deep. Water the soil so it's damp but not soaked. Place the pot at the bottom of the shoebox, on the opposite side from the hole you just cut.
3. Design the Maze: Cut two or three pieces of cardboard to act as partitions. They should be wide enough to almost touch the sides of the box, but leave a gap for the plant to grow around.
4. Install the Maze Walls: Using tape or a hot glue gun, secure the cardboard partitions inside the box. Stagger them so the plant has to grow around them to get to the light at the top. Look at it from the bottom up—does it create a zigzag path? Perfect!
5. Close it Up: Place the lid on the box and tape it shut to ensure no extra light gets in. Place the entire box in a location that gets plenty of sunlight, with the hole facing the window or light source.

Part 3: The Watch - Observation & Data Collection (Daily for 1-2 weeks)

Science is all about careful observation. For the next week or two, you will be a biologist collecting data.

1. Daily Check-in (5 mins): Each day, briefly open the lid of your box to check on your plant.
   • Is the soil dry? If so, add a small amount of water.
   • Has the seed sprouted?
   • What direction is the sprout growing?
2. Record Your Findings: In your Lab Notebook, create a daily log. Each day, write the date and your observations. Sketching the plant's progress is a fantastic way to document its growth and direction. Note how it navigates the maze you built!

Part 4: The Discovery - Analysis & Conclusion (Final Day - 30 mins)

Once your plant has reached the light source at the top of the box (or after about two weeks), it's time to analyze your results.

1. Final Observation: Carefully remove the lid and one side of the box to reveal the entire plant and its journey through the maze. Take a final sketch or a photo for your notebook.
2. Answer the Big Questions: In your Lab Notebook, write a "Conclusion" section. Answer the following questions in full sentences:
   • Was your hypothesis supported by your experiment? Explain why or why not, using your observations as evidence.
   • Describe the path your plant took to reach the light. How did it navigate the maze partitions?
   • Based on your results and the background information, explain the role of phototropism and auxin in your plant's survival.
   • What challenges did you face during this experiment? If you were to do it again, what would you change or test next?

Differentiation & Extension Activities

Want to take this even further? Try one of these advanced challenges!

• The Color Challenge: What if the light source was a different color? Design an experiment to test if plants prefer a certain color of light. You could use colored cellophane over the light hole.
• The Gravitropism Test: Plants don't just respond to light; they also respond to gravity (gravitropism). Roots grow down, and stems grow up. After your seed sprouts, what would happen if you laid the pot on its side? Design an experiment to investigate this.
• Maze Runner Race: Set up two identical mazes but use two different types of seeds. Which plant can solve the maze faster? This explores differences in growth rates between species.

Assessment

Your learning will be assessed based on the quality and completeness of your Lab Notebook. A great Lab Notebook will include:

• A clear hypothesis.
• Detailed daily observations, including sketches or photos.
• A thoughtful and well-reasoned conclusion that uses evidence from your observations to answer the analysis questions.
• Creative thinking and reflection on the experimental process.